1. Field of Invention
The present invention relates to a method for washing an actuator arm assembly for use with an information recording/reproducing unit such as a magnetic disk storage unit, an actuator arm assembly suitable for the washing method, and an information recording/reproducing unit.
2. Description of the Prior Art
FIG. 1 is a plan view of a conventional magnetic disk storage unit 10. A plurality of magnetic disks 11 are stacked at even spacings, mounted on a rotating shaft 19, and rotated at a fixed rotating speed. The magnetic disks use a front and a back side as recording areas respectively. An actuator arm assembly 21 hereinafter referred to as comb-type actuator arm assembly) includes a comb-type carriage 14 and a head/suspension assembly having a magnetic head 12 attached thereto is mounted so as to face the magnetic disk, and the rear end of the head/suspension assembly 13 is connected to an arm portion of the comb-type carriage 14. In the comb-type carriage 14, a coil support 22 is formed, and a coil 26 is fixed to the inside of it by a bonding agent. A permanent magnet is mounted in a voice coil motor portion 15, and the coil 26 is held in its magnetic field. A lead wire of the coil 26 and the lead wire connected to the magnetic head are connected to a control unit 17 through a flexible cable 16 and a circuit board 20. The control unit 17 feeds a controlled current to the coil 26 to swing the actuator arm assembly about a pivot shaft 18, thereby for positioning the magnetic head at a predetermined track position on the magnetic disk 11 along the direction indicated by arrow A. During the operation of the magnetic disk storage unit, air flow generated on the disk surface by the rotating magnetic disk 11 provides a floating force to the slider, and the head performs a data read/write to the magnetic disk while being spaced apart from the magnetic disk surface by a very small distance. Since the spacing between the head and the magnetic disk is very small, an error occurs in the head operation even if fine particulates stick to the magnetic disk surface. Accordingly, it is needed to maintain the inside of the magnetic disk storage unit in a clean environment, and in the manufacturing stage of the magnetic disk storage unit, the respective components are assembled in a clean room after washed by super-pure water or another solvent.
As one of the sources of particulates produced in the manufacturing stage, there is a soldering process. The flux used in the soldering vaporizes and sticks to the surrounding components. Accordingly, washing the components contaminated by the flux by the soldering is preferred for keeping the environment in the magnetic disk storage unit clean. In particular, this tendency is remarkable in the magnetic disk storage unit having a high recording density. Since a connection of the flexible cable 16 to the lead wire for the head is also provided by solder in the actuator arm assembly, it is preferred to wash the actuator arm assembly wholly after the soldering. However, since the actuator arm assembly includes the pivot 18 as a component and the pivot uses a lubricating oil in its inner bearing, the assembly cannot be immersed wholly in the super-pure water for washing. Accordingly, the washing of the actuator arm assembly needs to be performed after the completion of the soldering and before the mounting of the pivot.
FIG. 2 is a perspective view of the comb-type actuator arm assembly 21 of the magnetic disk storage unit of FIG. 1. A lead wire 31 is drawn out from a head 30, and soldered to the flexible cable 16 at a portion 32 of a connecting board 24. For simplicity, the lead wire 31 for the head is depicted only for the uppermost head/suspension assembly, and a lead wire is actually drawn out from each head in a similar manner. Further, from the beginning and the ending terminal of the coil 26, two lead wires 27 and 28 are drawn out and connected to the flexible cable 16 by solder. The comb-type carriage 14 is usually integrally molded by aluminum die casting. In the actuator arm assembly 21 shown in FIG. 2, when the lead wire 31 for the head and the lead wires 27 and 28 for the coil are connected to the flexible cable by solder on the connecting board, the pivot is not yet mounted into the shaft hole 33 of the comb-type carriage 14. Accordingly, the structure contaminated by flux, shown in FIG. 2, is washed wholly, and thereafter the pivot can be mounted in the clean room.
In recent years, an actuator arm assembly (hereinafter referred to as stacked actuator arm assembly) which does not use the comb-type carriage has been employed. In this actuator arm assembly, a head/suspension assembly is integrally formed from a portion on which a head is to be mounted to a portion to be inserted into a pivot shaft, and they are stacked with spacers sandwiched there between and fixed to the pivot. After the head/suspension assemblies and spacers are fixed to the pivot shaft, the lead wires from the heads and coil are connected to a flexible cable by solder on a connecting board. Accordingly, if the pivot is removed from the stacked head/suspension assemblies and spacers after the soldering, the stacked structure cannot be maintained, so the soldered connection is exposed to stress and may be peeled off. Thus, the pivot cannot be removed after the soldering.
Since the stacked actuator arm assembly needs to maintain the structure integral with the pivot after the soldering is completed on the connecting board, and therefor the assembly cannot be washed, a partial washing around the soldered connection has conventionally been performed so as not to adversely affect the lubricating oil of the pivot. However, it is not ensured that contaminated region due to flux is limited to the partial region partially washed, and thus particulates cannot be fully removed by the partial washing, producing a bottleneck in realizing a high-density magnetic disk storage unit.
Further, in assembling of the stacked actuator arm assembly, the stacked structure is fixed by screwing the pivot with a nut after aligning the head/suspension assemblies and spacers, but the rotational force of the nut screwed by a wrench may be transmitted to the head/suspension assemblies and spacers by friction to bring them out of alignment. If the alignment of the head/suspension assemblies is broken, the effective region dedicated to the disk recording is decreased, and if the alignment of the spacers is broken, the drive performance of the actuator by the VCM is adversely affected.
Accordingly, it is an object of the present invention to provide a method for washing a stacked actuator arm assembly wholly after the completion of the soldering.
It is a further object of the present invention to provide a stacked actuator arm assembly suitable for the above washing, in which the head/suspension assemblies are not put out of alignment when the pivot is mounted thereto.
It is still a further object of the present invention to provide a method for making a stacked actuator arm assembly.
It is still a further object of the present invention to provide an information recording/reproducing unit on which the above stacked actuator arm assembly is mounted, in which the recording area of the disks is not made decrease and the drive performance of the actuator is not reduced.